AvaloniaUI/Avalonia · error · InvalidOperationException

BeginInit was not called.

Error message

BeginInit was not called.

What it means

Error "BeginInit was not called." thrown in AvaloniaUI/Avalonia.

Solutions

1. Call BeginInit() before setting properties on the element and EndInit() afterwards.
2. Remove the EndInit() call if initialization was never started.

When it happens

Trigger: Raised when EndInit is called without a preceding BeginInit on a StyledElement. Defend by always pairing BeginInit/EndInit calls (typically via the initialization pattern in XAML loaders) and never calling EndInit directly.

Common situations: See trigger scenarios.

AI-assisted analysis of AvaloniaUI/Avalonia@11c5427268 (2026-08-13). Data as JSON: /api/errors/858f514dcd8adbec. Report an issue: GitHub.

Appendix: source

Thrown at src/Avalonia.Base/StyledElement.cs:359

        /// <inheritdoc/>
        IStyleHost? IStyleHost.StylingParent => (IStyleHost?)InheritanceParent;

        internal static ControlTheme InvalidTheme
            => s_invalidTheme ??= new();

        /// <inheritdoc/>
        public virtual void BeginInit()
        {
            ++_initCount;
        }

        /// <inheritdoc/>
        public virtual void EndInit()
        {
            if (_initCount == 0)
            {
                throw new InvalidOperationException("BeginInit was not called.");
            }

            if (--_initCount == 0 && _logicalRoot is not null)
            {
                ApplyStyling();
                InitializeIfNeeded();
            }
        }

        /// <summary>
        /// Applies styling to the control if the control is initialized and styling is not
        /// already applied.
        /// </summary>
        /// <remarks>
        /// The styling system will automatically apply styling when required, so it should not
        /// usually be necessary to call this method manually.
        /// </remarks>
        /// <returns>

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